This invention relates to ink jet printheads. More particularly, this invention relates to a nozzle arrangement for an ink jet printhead that includes a shape memory actuator.
The Applicant has invented an ink jet printhead that is capable of generating text and images at a resolution of up to 1600 dpi.
In order to achieve this, the Applicant has made extensive use of micro electro-mechanical systems technology. In particular, the Applicant has developed integrated circuit fabrication techniques suitable for the manufacture of such printheads. The Applicant has filed a large number of patent applications in this field, many of which have now been allowed.
The printheads developed by the Applicant can include up to 84000 nozzle arrangements. Each nozzle arrangement has at least one moving component that serves to eject ink from a nozzle chamber. The components usually either act directly on the ink or act on a closure which serves to permit or inhibit the ejection of ink from the nozzle chamber.
The moving components within the printheads are microscopically dimensioned. This is necessary, given the large number of nozzle arrangements per printhead. The Applicant has spent a substantial amount of time and effort overcoming the difficulties associated with achieving effective movement of such components in order to eject ink.
The high density of nozzle arrangements precludes the use of heating the ink to an extent necessary to achieve the ejection of the ink, a technique which has been developed for scanning ink jet printheads. This form of ink ejection is possible with such ink jet printheads since the nozzle arrangements are positioned on a printhead that physically scans the print medium. Thus, the number of nozzle arrangements required is substantially less. Applicant has found that the heat build-up in a printhead incorporating up to 84000 nozzle arrangements would simply be too high for the printhead to operate efficiently, if at all.
It is also important to note that the high number of nozzle arrangements makes it essential that energy use is kept to a minimum. Applicant is aware of a number of prior art configurations which utilize piezoelectric expansion of metal to achieve buckling and subsequent drop ejection. Again, with the high number of nozzle arrangements used for the page width printhead of this invention, such configurations have excessive energy demands.
The Applicant has found that phase change characteristics of particular materials can be utilized efficiently in such ink jet printheads. Accordingly, the Applicant has applied this principle and has conceived this invention to address the problems associated with the prior art configurations mentioned above.
According to a first aspect of the invention, there is provided a nozzle arrangement for an ink jet printhead, the nozzle arrangement comprising
a substrate;
nozzle chamber walls arranged on the substrate to define a nozzle chamber of the nozzle arrangement; and
an actuator for ejecting ink from the nozzle chamber, the actuator comprising:
at least one actuating member, at least a portion of the, or each, actuating member being in the form of a shape memory material which is capable of generating movement of the, or each, actuating member between pre-operative and post-operative positions when the shape memory material undergoes a structural change to or from a trained shape under predetermined conditions to eject ink from the nozzle chamber; and
a transformation mechanism that is operatively arranged with respect to the shape memory material to generate said predetermined conditions.
According to a second aspect of the invention, there is provided an ink jet printhead that comprises:
a substrate; and
at least one nozzle arrangement positioned on the substrate, the, or each, nozzle arrangement comprising:
nozzle chamber walls arranged on the substrate to define a nozzle chamber of the nozzle arrangement; and
an actuator for ejecting ink from the nozzle chamber, the actuator comprising:
at least one actuating member, at least a portion of, the, or each, actuating member being in the form of a shape memory material which is capable of generating movement of the, or each, actuating member between pre-operative and post-operative positions when the shape memory material undergoes a structural change to or from a trained shape under predetermined conditions to eject ink from the nozzle chamber; and
a transformation mechanism that is operatively arranged with respect to the shape memory material to generate said predetermined conditions.